TY - THES

T1 - Preparation and characterization of (La,Ca,Sr)(Fe,Co)O3-δ cathodes for solid oxide fuel cells

AU - Micu-Budisteanu, Mario

N1 - embargoed until null

PY - 2021

Y1 - 2021

N2 - In this work, novel mixed ionic-electronic conducting cathode materials for solid oxide fuel cells are investigated with respect to crystal structure, as well as mass- and charge transport properties. Recent studies on compounds from the series (La,Ca)FeO3-δ show that these materials exhibit exceptionally fast oxygen exchange kinetics and high long-term stability under critical operating conditions (e.g. SO2-poisoning). New compounds, obtained by substitution of La0.8Ca0.2FeO3-δ with Sr or Co, are synthesized and characterized. In cooperation with Forschungszentrum Jülich (FZJ), cells with air electrodes fabricated from materials developed at Montanuniversitaet Leoben (MUL) are prepared and electrochemically characterized. In addition to the perovskite La0.8Ca0.2FeO3-δ (LCF82), which has been well characterized with regard to material properties and exhibits fast oxygen exchange kinetics and good stability against SO2-poisoning, materials with Sr- or Co-substitution are investigated. The compounds La0.6Ca0.2Sr0.2FeO3-δ (LCSF622) and La0.8Ca0.2Fe0.8Co0.2O3-δ (LCFC8282) are studied with respect to phase purity and crystal structure by means of XRD and Rietveld refinement. Thermal expansion coefficients are determined by dilatometry. Further, the electronic conductivity and the oxygen exchange kinetics are investigated by means of dc-conductivity and dc conductivity relaxation measurements. Subsequently, screen-printing pastes are fabricated and rheologically optimized, in order to manufacture porous electrodes on symmetrical and anode-supported cells. The cells are characterized by electrochemical impedance spectroscopy and current-voltage curves. Post-mortem analyses provide further insights into the sintering behavior of the porous electrodes, their microstructure, and layer adhesion on the electrolyte.

AB - In this work, novel mixed ionic-electronic conducting cathode materials for solid oxide fuel cells are investigated with respect to crystal structure, as well as mass- and charge transport properties. Recent studies on compounds from the series (La,Ca)FeO3-δ show that these materials exhibit exceptionally fast oxygen exchange kinetics and high long-term stability under critical operating conditions (e.g. SO2-poisoning). New compounds, obtained by substitution of La0.8Ca0.2FeO3-δ with Sr or Co, are synthesized and characterized. In cooperation with Forschungszentrum Jülich (FZJ), cells with air electrodes fabricated from materials developed at Montanuniversitaet Leoben (MUL) are prepared and electrochemically characterized. In addition to the perovskite La0.8Ca0.2FeO3-δ (LCF82), which has been well characterized with regard to material properties and exhibits fast oxygen exchange kinetics and good stability against SO2-poisoning, materials with Sr- or Co-substitution are investigated. The compounds La0.6Ca0.2Sr0.2FeO3-δ (LCSF622) and La0.8Ca0.2Fe0.8Co0.2O3-δ (LCFC8282) are studied with respect to phase purity and crystal structure by means of XRD and Rietveld refinement. Thermal expansion coefficients are determined by dilatometry. Further, the electronic conductivity and the oxygen exchange kinetics are investigated by means of dc-conductivity and dc conductivity relaxation measurements. Subsequently, screen-printing pastes are fabricated and rheologically optimized, in order to manufacture porous electrodes on symmetrical and anode-supported cells. The cells are characterized by electrochemical impedance spectroscopy and current-voltage curves. Post-mortem analyses provide further insights into the sintering behavior of the porous electrodes, their microstructure, and layer adhesion on the electrolyte.

KW - Solid Oxide Fuel Cell

KW - Cathode

KW - SOFC

KW - Hochtemperaturbrennstoffzelle

KW - Kathode

KW - SOFC

M3 - Master's Thesis

ER -